Introduction The evolution of computed tomography (CT) findings in patients with mild coronavirus disease 2019 (COVID-19) pneumonia has not been described in detail. A large-scale longitudinal study is urgently required. Methods We analyzed 606 CT scans of 182 patients. The dynamic evolution of CT scores was evaluated using two staging methods: one was divided into 10 periods based on decile intervals, and the other was one stage per week. Moreover, the latter was used to evaluate the dynamic evolution of imaging performance. A published severity scoring system was used to compare findings of the two methods. Results In the dynamic evolution of 10 stages, the total lesion CT score peaked during stage 3 (9-11 days) and stage 6 (17-18 days), with scores = 7.19 +/- 3.66 and 8.00 +/- 4.57, respectively. The consolidation score peaked during stage 6 (17-18 days; score = 2.72 +/- 3.07). In contrast, when a 1-week interval was used and time was divided into five stages, the total lesion score peaked during week 3 (score = 7.3 +/- 4.15). The consolidation score peaked during week 2 (score = 2.54 +/- 3.25). The predominant CT patterns differed significantly during each stage (P < 0.01). Ground-glass opacities (GGO), with an increased trend during week 3 and beyond, was the most common pattern in each stage (33-46%). The second most common patterns during week 1 were GGO and consolidation (24%). The linear opacity pattern with an increased trend was the second most common pattern during week 2 and beyond (21-32%). Conclusions The total lesion score of mild COVID-19 pneumonia peaked 17-18 days after disease onset. The consolidation scores objectively reflected the severity of the lung involvement compared with total lesion scores. Each temporal stage of mild COVID-19 pneumonia mainly manifested as GGO pattern. Moreover, good prognosis may be associated with increases in the proportions of the GGO and linear opacity patterns during the later stage of disease.